The present invention is directed to an expansion anchor assembly for use in boreholes formed in a receiving material and the assembly includes an expansion sleeve, a tie rod with an expansion cone located on one end of the tie rod and with a cone sleeve positioned between the expansion cone and the expansion sleeve. For effecting the expanding action, the tie rod is pulled in the direction out of the borehole. The radially outer surface of the cone sleeve and the expansion cone each have a different cone angle.
Considerable expansion dimensions are required for expansion anchors used in tensile zone. In the past the attempt to use known anchors with an expansion sleeve, a cone sleeve and an expansion cone have not been effective. In such a known expansion anchor, the expanding process takes place as the expansion cone is drawn out of the borehole in the direction opposite to the insertion direction of the anchor. The expansion cone acts on the cone sleeve which moves into the expansion sleeve. After the cone sleeve is moved into the expansion sleeve and a first expansion of the expansion sleeve is effected, the expansion cone moves into the cone sleeve and causes an additional expansion of the expansion sleeve along with widening of the cone sleeve. This sequence of the expansion process is obtained with the cone sleeve having a smaller cone angle than the expansion cone.
A disadvantage of this known expansion anchor is that the cone sleeve moves into the expansion sleeve at various depths based on the strength or density of the receiving material, before the expansion cone takes effect. Particularly in receiving materials having great strength and with narrow boreholes, the cone sleeve moves into the expansion sleeve only slightly and effects a relatively slight expansion of the expansion sleeve. Subsequently, when the expansion cone is drawn into the cone sleeve, the cone sleeve is expanded only in the region projecting from the expansion sleeve with the result that no appreciable additional expansion of the expansion sleeve takes place. When employed in lower strength receiving material and in wider boreholes, less resistance is present against the movement of the cone sleeve so that it is completely drawn into the expansion sleeve without expansion of the cone sleeve resulting due to the movement of the expansion cone. Therefore, in both of the situations described, and especially when used in tensile zones subject to fracture, this known expansion anchor has a low expansion characteristic.